The invention relates to a drive unit including an electric motor for driving a cooling fan of a motor vehicle engine and for driving a hydraulic pump.
Drive units of this type are known, for example, from DE 40 14 175 A1. These known drive units include an electric motor serving as the drive for an oil pump and also for the cooling fan, the driveshafts of the oil pump and cooling fan being arranged coaxially and each being connected to an end of the electric motor driveshaft which project from the opposite sides of the electric motor. Such arrangements eliminate the need for additional electric motors for driving the individual components. In addition to omitting the need for an electric motor, this also has the advantage that the weight of the drives is reduced. Since with these arrangements both, the oil pump and the cooling fan, are operated continuously, the electric motor for driving them must, however, be designed to be sufficiently powerful.
DE-OS 14 76 110 furthermore discloses an arrangement with an electric motor as a drive device for all the accessory units of a motor vehicle engine, wherein the electric motor is powered by the vehicle electrical circuit and is running at a constant speed independently of the internal combustion engine. In this improved arrangement the accessories and the cooling fan for the engine coolant may all be driven at the same time when this is necessary because of a relatively high coolant temperature. Consequently, the electric-motor drive is designed to be sufficiently powerful to be able to drive all the accessory units.
It is known in principle, for example, from DE 31 10 591 C2 to drive a pump or a fan alternately by an electric motor by changing the direction of rotation of the electric motor. Then however, the motor needs to be stopped and again accelerated in the reverse for this purpose. This not only consumes power but also requires a relatively powerful and expensive motor and thus increases weight and costs which should be maintained as low as possible.
It is the object of the present invention to provide a drive unit which, although having at least two different accessory units, can be driven by an electric motor which need not, however, be dimensioned to be able to drive the accessory units at the same time.